Light emitting device

ABSTRACT

There is provided a light emitting device of a simpler structure, capable of ensuring a broad light emitting area and a high light emitting efficiency, while manufactured in a simplified and economically efficient process. The light emitting device including: a semiconductor layer; an active layer formed on the semiconductor layer, the active layer comprising at least one of a quantum well structure, a quantum dot and a quantum line; an insulating layer formed on the active layer; and a metal layer formed on the insulating layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.12/000,360, filed on Dec. 12, 2007, now U.S. Pat. No. 8,030,664 whichclaims the priorities of Korean Patent Application No. 2006-129003 filedon Dec. 15, 2006 and Korean Patent Application No. 2006-129004 filed onDec. 15, 2006, in the Korean Intellectual Property Office, the entirecontents of each of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device, and moreparticularly, a light emitting device of a simpler structure capable ofensuring a broad light emitting area and a high light emittingefficiency, while manufactured in a simplified and economicallyefficient process.

2. Description of the Related Art

In a light emitting device, a material contained therein emits light.For example, a light emitting device may have a semiconductor junctionusing a diode to convert energy generated by recombination of holes andelectrons into light.

A light emitting diode (LED) of a semiconductor junction structurecurrently manufactured is generally formed by junction of a p-typesemiconductor and an n-type semiconductor. In the LED of thesemiconductor junction structure, an active layer is disposed betweenthe two semiconductors to emit light tuned to a desired wavelength.

For example, in manufacturing a compound semiconductor LED using atleast two elements such as GaAs, typically a heterogeneous substrate isemployed to grow the semiconductor epitaxially. Here, crystals grownexperience defects due to stress caused by mismatch of lattice constantand thermal expansion coefficient.

Especially, a sapphire substrate, when employed in a nitridesemiconductor, results in considerable defects due to a great mismatchbetween a nitride and the substrate, thereby degrading light emittingcharacteristics of a light emitting device manufactured.

Also, in the LED of the semiconductor junction structure, the n-typesemiconductor and the p-type semiconductor should be grown on onesubstrate, which is, however, a difficult process.

The LED has been recently fabricated as a nanorod or a nanowire to beutilized as the light emitting device. For example, an n-type nanorodand a p-type nanorod are formed to cross each other in order to emitlight at an intersection. Here, the nanoscale device emits blue-shiftedlight owing to stress induced by decrease in a diameter thereof. Each ofthe nanorods, even when formed of a material with an identicalcomposition, may have a light emitting wavelength varied by a diameteror a length thereof.

In addition to the LED, efforts have been under way to utilize as alight emitting device a Metal Insulator Semiconductor (MIS) formed of ametal-insulator-semiconductor in use for a conventional capacitor. TheMIS device features a simpler structure due to a fewer number of layersrequired than the aforesaid LED light emitting device, therebysimplifying a manufacturing process and saving manufacturing costs.

FIG. 1A is a cross-sectional view illustrating a conventional lightemitting device 10 using an MIS structure. Hereinafter, the lightemitting device 10 is assumed to be an m-i-p type light emitting devicein which a semiconductor layer 11 is a p-type semiconductor.

The light emitting device 10 includes a semiconductor layer 11, aninsulating layer 11 and a metal layer 15, and an electrode 17 formedunderneath the semiconductor layer 11. An area A of the semiconductorlayer 11 experiences recombination of holes and electrons by tunnelingeffects of the electrons, thereby generating light.

FIG. 1B illustrates an energy diagram illustrating such a light emittingmechanism. Referring to FIG. 1B, energy levels are plotted in a casewhere a minus (−) voltage is applied to the metal layer 15 and a plus(+) voltage is applied to the semiconductor layer 11.

With the minus (−) voltage applied to the metal layer 15, electrons e⁻migrate through the insulating layer 13 by tunneling effects.Subsequently, the electrons e⁻ reach the semiconductor layer 11 and thenrecombine with holes h⁺ in a valence band of the semiconductor layer 11to generate photons.

However, in this MIS light emitting device, light generated when thetunneled electrons e⁻ reach the semiconductor layer 11 to recombine withthe holes h⁺, is lower in light emitting efficiency than other lightemitting devices, thus required to be increased in light emittingefficiency.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a light emitting device of asimpler structure capable of ensuring a broad light emitting area and ahigh light emitting efficiency, while manufactured in a simplified andan economically efficient process.

According to an aspect of the present invention, there is provided alight emitting device including: a semiconductor layer; an active layerformed on the semiconductor layer, the active layer comprising at leastone of a quantum well structure, a quantum dot and a quantum line; aninsulating layer formed on the active layer; and a metal layer formed onthe insulating layer.

The semiconductor layer may be formed of one of a GaN-basedsemiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, aGaP-based semiconductor, and a GaAsP-based semiconductor.

The active layer may include at least one layer. The active layer mayinclude a quantum well structure, wherein the quantum well structure maybe one of a single quantum well structure and a multiple quantum wellstructure.

The active layer may include a plurality of quantum dots, wherein thequantum dots may include one of a group III-V compound semiconductor anda group II-VI compound semiconductor. The quantum dots may be formed ofa GaN-based compound.

The active layer may include a plurality of quantum lines, wherein thequantum lines may be formed of one of a group III-V compoundsemiconductor and a group II-VI compound semiconductor.

The active layer may include the quantum lines and an organic compoundsurrounding the quantum lines.

An outermost layer in a propagation direction of light from the lightemitting device may have microstructure formed on a surface thereof. Thesemiconductor layer, the insulating layer and the metal layer may havemicrostructures formed on surfaces thereof, respectively.

The metal layer may have a plurality of holes formed in a surfacethereof. The holes may be extended to a portion between a top of theinsulating layer and a top of the active layer.

The light emitting device may further include a photonic crystalstructure formed on one surface thereof. The holes may have a diameterand a spacing of 200 nm to 1000 nm, respectively.

The light emitting device may further include a substrate, wherein astack having the semiconductor layer, the active layer, the insulatinglayer and the metal layer sequentially stacked is formed on thesubstrate, wherein the stack is a nanowire structure. The substrate maybe provided thereon with a nanowire array including a plurality ofnanowire structures.

The active layer may include one of a quantum well structure and aquantum dot. The active layer may include at least one layer. The activelayer may include a quantum well structure, wherein the quantum wellstructure may be one of a single quantum well structure and a multiplequantum well structure.

The active layer may include at least one quantum dot, wherein thequantum dot may be formed of a group III-V compound semiconductor. Thequantum dot may be formed of a GaN-based compound. The active layer mayinclude at least one quantum dot, wherein the quantum dot may be formedof a group II-VI compound semiconductor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1A is a cross-sectional view illustrating a conventional lightemitting device with an MIS structure;

FIG. 1B is an energy diagram illustrating a light emitting device shownin FIG. 1A;

FIG. 2 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention;

FIG. 3 is an energy diagram illustrating the light emitting device shownin FIG. 2;

FIG. 4 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention;

FIG. 5 is an energy diagram illustrating the light emitting device shownin FIG. 4;

FIG. 6 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention;

FIG. 7 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention;

FIG. 8 is a cross-sectional view illustrating a light emitting devicehaving microstructures formed thereon according to an exemplaryembodiment of the invention;

FIG. 9 is a cross-sectional view illustrating a light emitting devicehaving microstructures formed thereon according to an exemplaryembodiment of the invention;

FIG. 10 is a cross-sectional view illustrating a light emitting devicehaving holes formed therein to define a photonic crystal structure onone surface thereof according to an exemplary embodiment of theinvention;

FIG. 11 is a cross-sectional view illustrating a light emitting deviceaccording an exemplary embodiment of the invention;

FIG. 12 is a view illustrating a three dimensional shape of the lightemitting device shown in FIG. 11;

FIG. 13 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention; and

FIG. 14 is a view illustrating a three dimensional shape of the lightemitting device shown in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth therein. Rather theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art.

FIG. 2 is a cross-sectional view illustrating a light emitting device100 according to an exemplary embodiment of the invention.

The light emitting device 100 of the present embodiment includes asemiconductor layer 110, an active layer 120 formed on the semiconductorlayer 110 to include at least one of a quantum well structure, a quantumdot and a quantum line, an insulating layer 130 formed on the activelayer 120 and a metal layer 150 formed on the insulating layer 130.

The light emitting device 100 includes the active layer 120 between thesemiconductor layer 110 and the insulating layer 130.

The semiconductor layer 110 may be formed of one of a GaN-basedsemiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, aGaP-based semiconductor and a GaAsP-based semiconductor.

The active layer 120 allows active emission of light from the lightemitting device 100. To activate light emission, the active layer 120may include at least one of the quantum well structure, the quantum dotand the quantum line. The active layer 120 may be formed of anystructure defining the quantum well structure. For example, the activelayer 120 may be formed of a GaN-based semiconductor. The activationfunction of the active layer 120 will be described with reference toFIG. 3.

The insulating layer 130 may be formed of a nitride or an oxide, andhave a thickness of about 1 nm to 10 nm in view of tunneling ofelectrons e⁻ from the metal layer 150. Also, the insulating layer shouldhave an energy band gap greater than a light emitting wavelength so asnot to absorb photons generated in the semiconductor layer 110.

The metal layer 150 may be a transparent electrode transmitting light ora barrier metal reflecting light.

FIG. 3 is an energy diagram of the light emitting device shown in FIG.2. Hereinafter, the same components as described above will not beexplained further.

When a minus (−) voltage is applied to the metal layer M, the electronse⁻ tunnel through the insulating layer I. The electrons e⁻ migratingthrough the insulating layer 130 encounter the quantum well structuredefined by the active layer 120. Accordingly, the electrons e⁻ recombinewith holes h⁺ in the quantum well structure to generate photons.

The quantum well structure is formed of at least two materials havingenergy band gaps different from each other. In the quantum wellstructure, the active layer 120 having a band gap different from thoseof the insulating layer 130 and the semiconductor layer 110,respectively is disposed therebetween to assure higher quantumconfinement effect. Consequently, the quantum well structure exhibitshigh photoluminescence.

That is, the quantum well structure defined by the active layer 120allows the electrons e⁻ to be recombined with the holes h⁺ more easily,thereby enhancing light emitting efficiency.

Moreover, the quantum well structure may be one of a single wellstructure and a multiple well structure. Referring to FIG. 3, thequantum well structure represents a single well structure. A desiredtype of the quantum well structure can be controlled appropriately byadjusting the active layer. Hereinafter, the active layer 120 has amultiple well structure as the quantum well structure.

FIG. 4 is a cross-sectional view illustrating a light emitting device200 according to an exemplary embodiment of the invention.

Referring to FIG. 4, an active layer 220 disposed between asemiconductor layer 210 and an insulating layer 230 of the lightemitting device 200 may include at least one layer. The active layer 220is configured as a multilayer structure and thus may define a pluralityof quantum well structures.

To form the active layer 220, a layer representing a quantum wellstructure and a layer representing an energy barrier may be stackedalternately. For example, the active layer 220 may include a GaN layerrepresenting the quantum well structure and an AlGaN layer representinga barrier layer stacked alternately. The quantum well structure and thebarrier layer may be stacked in an appropriate number of alternations bythose skilled in the art in view of light emission efficiency.

FIG. 5 is an energy diagram of the light emitting device 200 shown inFIG. 4.

Referring to FIG. 5, the active layer 220 is formed of five layers, withthe quantum well structure and the barrier layer stacked alternately 2.5times. This allows a plurality of quantum well structures to be formedon a contact area between the insulating layer 230 and the semiconductorlayer 210, thus further enhancing light emitting efficiency of the lightemitting device 200.

FIG. 6 is a cross-sectional view illustrating a light emitting device300 according to an exemplary embodiment of the invention, in which anactive layer 320 includes quantum dots 321. FIG. 7 is a cross-sectionalview illustrating a light emitting device 400 according to an exemplaryembodiment of the invention, in which an active layer 420 includesquantum lines 421.

First, referring to FIG. 6, the active layer 320 includes the quantumdots 321. The quantum dots 321 may be formed of a GaN-based compound. Aportion 322 of the active layer 320 excluding the quantum dots 321 maybe formed of an insulator or a semiconductor.

The quantum dots 321 each have a diameter of several nm and are arrangedthree-dimensionally overall, thus ensuring high quantum confinementeffect. This leads to effective confinement of electrons, consequentlyboosting light emission efficiency of the light emitting device 300.

Referring to FIG. 7, the active layer 420 includes the quantum lines421. The quantum lines 421 are formed in the active layer 420, between asemiconductor layer 410 and an insulating layer 430. The quantum lines421 may be formed of a semiconductor, e.g., one of a group III-Vcompound semiconductor and a group II-VI compound semiconductor. Whenthe quantum lines 421 are formed of the group II-VI semiconductor, aportion of the active layer 422 excluding the quantum lines 421 may beformed of an organic semiconductor.

FIGS. 8 to 10 are cross-sectional views illustrating light emittingdevices having microstructures formed thereon according to exemplaryembodiments of the invention, respectively.

FIG. 8 illustrates a light emitting device 500 having microstructures551 formed on one surface thereof. Especially, the microstructures areformed on a metal layer 550, an insulating layer 530 and a semiconductorlayer 510, respectively.

The microstructures are not formed on the active layer 520. Themicrostructures, when formed on the active layer 520 may impair theactive layer 520 too much and affect a light emitting surface directly.

With the microstructures formed, light emitted is free from adversefactors for light extraction efficiency such as total reflection on thesurface and effectively scattered. This improves overall lightextraction efficiency of the light emitting device 500.

Referring to FIG. 9, microstructures 611 are formed on a bottom of alight emitting device 600. This is because the microstructures formed ona surface in a propagation direction of light may enhance lightextraction efficiency.

The microstructures may be formed on a metal layer 650, an insulatinglayer 630 and a semiconductor layer 610, respectively but particularlyon a surface of an outermost layer in a propagation direction of light.

Therefore, in a case where the metal layer 550 is the outermost layer ina propagation direction of light, as shown in FIG. 8, themicrostructures are formed on at least the metal layer 550. Also, in acase where the semiconductor layer 610 is the outermost layer in apropagation direction of light, as shown in FIG. 9, the microstructuresare formed on at least the semiconductor layer 610.

FIG. 10 illustrates a light emitting device 700 in which microstructuresare not formed on corresponding layers as in FIGS. 8 and 9 but moreefficient structures than the microstructures are formed.

A plurality of holes H are formed uniformly with a predetermined depthin a surface of a metal layer 750. The holes each H are extended toreach a partial depth of the insulating layer 730, thereby exposing theinsulating layer 730 from bottoms of the holes H. The light emittingdevice structured as above can represent a photonic crystal structure.Photonic crystals are composed of media with different refractiveindexes arranged regularly like crystals. These photonic crystals allowextraction of light having a wavelength that is multiple times awavelength of light, thereby further enhancing optical extractionefficiency.

The holes H may have a diameter and a spacing of about 200 nm to 1000nm, respectively, in view of effective photonic crystal structure.

The holes H can be formed by an appropriate process after fabricatingthe light emitting device 700. For example, the holes H may be formed byetching.

In a case where the holes each H are extended to reach only the metallayer 750 or a partial depth of the metal layer 750 instead of theinsulating layer 730, the light emitting device with these holesconstitutes a surface plasmon structure, not a photonic crystalstructure. Also, the holes H, if extended to the active layer 730, maydamage the active layer 730.

The surface plasmon is a wave of electron density moving along aninterface between a conductor and a non-conductor. This surface plasmonmay be generated by incident light and resonance occurs at a certainincident angle satisfying resonance conditions. This is referred to as asurface plasmon resonance.

Under resonance conditions where momentums between incident photons andthe surface plasmon are identical to each other, energy of lightincident as the surface plasmon is greatly excited is absorbed as aradiation energy or a thermal energy. This consequently minimizesintensity of the light passing through a metal of the metal layer 750.Therefore, the holes H formed to reach only the metal layer 750 or apartial depth of the metal layer 750 may undesirably satisfy conditionsfor formation of this surface plasmon.

Referring to FIG. 10, the metal layer 750 is the outermost layer in apropagation direction of light. However, as shown in FIG. 9, in a casewhere the semiconductor layer 610 is the outermost layer in apropagation direction of light, it is evident that the holes may beformed in the semiconductor layer.

FIG. 11 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention.

The light emitting device 800 includes a substrate 810 and a nanowirearray including nanowire structures 820 each having a metal layer 826,an insulating layer 824 and a semiconductor layer 822 sequentiallystacked on the substrate 810. The nanowire array is formed on thesubstrate 810 and an electrode 828 is formed on a top of the nanowirearray to apply a voltage for driving the light emitting device 800.

The nanowire structures 820 are formed top-down or bottom-up on thesubstrate 810. The substrate 810 may adopt any substrate matching ine.g., lattice constant with the nanowire structures 820. For example,the substrate 810 may employ a sapphire substrate or a SiC substrate,which has a GaN layer on a top thereof.

The nanowire structures 820 are formed on the substrate 810. Each of thenanowire structures 820 includes the semiconductor layer 822, theinsulating layer 824 and the metal layer 826.

This nanowire structure 820 may feature a metal insulator semiconductor(MIS) structure.

The semiconductor layer 822 may be formed of a semiconductor for use ina general light emitting device of an MIS structure. Particularly, thesemiconductor layer 822 may be formed of a direct-type compoundsemiconductor. The semiconductor layer 822 may be formed of one of ap-type semiconductor and an n-type semiconductor. For example, thesemiconductor layer 822 may be formed of at least one of a GaN-basedsemiconductor, a ZnO-based semiconductor, a GaAs-based semiconductorhaving a composition expressed by In_(x)Al_(y)Ga_(1-x-y)N, where 0≦x≦1,0≦y≦1, and 0≦x+y≦1, a GaP-based semiconductor, and a GaAsP-basedsemiconductor.

The insulating layer 824 may be formed of a nitride or an oxide, andhave a thickness of about 1 nm to 10 nm in view of tunneling ofelectrons e⁻ from the metal layer 826. Also, the insulating layer 824should have an energy band gap greater than a light emitting wavelengthso as not to absorb photons generated in the semiconductor layer 822.

The metal layer 826 may be formed of a transparent electrodetransmitting light or a barrier metal reflecting light.

The semiconductor layers 822, the insulating layers 824 and the metallayers 826 each are stacked to constitute the respective nanowirestructures as the MIS devices. The nanowire structures 820 are arrangedon the substrate 810 regularly or irregularly to form the nanowirearray.

A ‘nanorod’ denotes a rod-shaped material having a diameter of severalnm to tens of nm. A ‘nanowire’ is shaped as an elongated line which islongitudinally greater than the nanorod.

The nanowire can be largely manufactured by top-down and bottom-downmethods.

In the top-down method, a material for the nanowire is etched to formanano structure. However, in this method, the material can be nano-scaledonly to tens of nm, while manufacturing costs are increased with furthersize reduction of the material. This has led to development of manybottom-down methods.

Examples of the bottom-down method include an Anodic Aluminum Oxidetemplate (AAO template) and a Vapor-liquid-Liquid-Solid phase (VLSphase).

In the AAO template method, aluminum is employed due to uniquecharacteristics thereof. That is, aluminum forms an array of poresduring an oxidization process for forming an oxidized aluminum.

Here, the pores have a diameter of tens of nm to hundreds of nmdepending on density of an acid solution and a voltage during anoxidized process of the aluminum, and a length of μm. Therefore, whenother materials are filled in the pores by physical and chemical vapordeposition using the AAO template, nanowires having the diameter andlength identical to those of the pores can be manufactured.

The VLS method is the surest way to manufacture the nanowires of asingle crystal structure in a large quantity, out of vapor phasemethods. First, a starting material of a gas state is melted by a liquiddroplet of a metal catalyst sized nm. This allows generation of nucleiand growth of single crystal rods. Then the single crystal rods arecontinually grown into nanowires.

In the VLS method, the growth of the nanowires is regulated by variousmethods. Each of the nanowires has a diameter determined according tosize of catalyst particles. Thus, a smaller droplet of the catalystensures a thinner nanowire. Moreover, the nanowires may have a lengthregulated by a growth time.

Meanwhile, the MIS devices configured as the nanowire structures arearranged on the substrate 810. With a voltage applied, each of thenanowire structures emits light.

Filled portions 828 are defined between the nanowire structures 820which are formed between the substrate 810 and the electrode 830, andmay be an air. Alternatively, the filled portions 828 may be atransparent polymer resin which does not affect light emission of thenanowire structures 820.

The electrode 830 may be disposed on a top of the nanowire array toapply a voltage to the light emitting device.

FIG. 12 is a view illustrating a three-dimensional shape of the lightemitting device shown in FIG. 11. The nanowire structures 820 arearranged on the substrate 810. Each of the nanowire structures 820includes the semiconductor layer 822, the insulating layer 824 and themetal layer 826. The Filled portions 828 and the electrode 830 areomitted.

The nanowire structure 820 is shaped as a wire and this nano-scale wireshape increases quantum confinement effect and broadens a light emittingsurface, thereby increasing light emitting efficiency.

FIG. 13 is a cross-sectional view illustrating a light emitting deviceaccording to an exemplary embodiment of the invention.

The light emitting device 900 includes a substrate 910, nanowirestructures 920, and filled portions 928, and an electrode disposed on atop of a nanowire array including the nanowire array structures 920 toapply a voltage. The nanowire structures 920 of the nanowire array eachmay further include an active layer 923 between an insulating layer 924and a semiconductor layer 922.

The active layer 923 allows active emission of light from the nano wirestructures 920. To activate light emission, the active layer 923 mayfurther include at least one of a quantum well structure and a quantumdot. The active layer 923 may be formed of any material capable ofrepresenting the quantum well structure. For example, the active layer923 may be formed of a GaN-based semiconductor having a compositionexpressed by In_(x)Al_(y)Ga_(1-x-y)N, where 0≦x≦1, 0≦y≦1, and 0≦x+y≦1.

FIG. 14 is a view illustrating a three-dimensional shape of the lightemitting device shown in FIG. 13. The nanowire structures 920 arearranged on the substrate 910 and each of the nanowire structures 920includes the semiconductor layer 922, the active layer 923, theinsulating layer 924 and the metal layer 926. The Filled portions 928and the electrode 930 are omitted.

The light emitting device configured as a nanowire structure asdescribed hereinabove, increases light emitting efficiency, and theactive layer with a quantum well structure or quantum dot furtherenhances light emitting efficiency.

As set forth above, according to exemplary embodiments of the invention,the light emitting device is of a simpler structure than a conventionalone, thus ensuring an economically efficient manufacturing process.

Also, the light emitting device does not need to have both a p-typesemiconductor and an n-type semiconductor formed therein, but may beprovided with only one of the two. This accordingly simplifies aprocess.

In addition, the light emitting device exhibits a broader light emittingarea than a planar-type structure. Moreover, a quantum well structure, aquantum dot or a quantum line is provided in a semiconductor layer andan insulating layer to increase light emitting efficiency.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

What is claimed is:
 1. A light emitting device comprising: asemiconductor layer; an active layer formed on the semiconductor layer,the active layer including a plurality of quantum dots, a plurality ofquantum well structures, or a plurality of quantum lines; an insulatinglayer formed on the active layer; and a metal layer formed on theinsulating layer, wherein the semiconductor layer, the insulating layerand the metal layer have microstructures disposed on surfaces thereof,respectively.
 2. The light emitting device of claim 1, wherein theactive layer comprises a plurality of quantum dots, and the plurality ofquantum dots comprise a GaN-based compound.
 3. The light emitting deviceof claim 1, wherein the active layer comprises a plurality of quantumlines, and the plurality of quantum lines comprise at least one of agroup III-V compound semiconductor and a group II-VI compoundsemiconductor.
 4. The light emitting device of claim 3, furthercomprising: an organic compound surrounding the plurality quantum lines.5. A light emitting device comprising: a semiconductor layer; an activelayer formed on the semiconductor layer, the active layer including aplurality of quantum dots, a plurality of quantum lines, or a pluralityof quantum well structures; an insulating layer formed on the activelayer; and a metal layer formed on the insulating layer, the metal layerhaving a plurality of holes formed in a surface thereof, wherein, if theactive layer includes quantum dots, the quantum dots comprise at leastone of a group III-V compound semiconductor and a group II-VI compoundsemiconductor, wherein the holes are extended to a portion between a topof the insulating layer and a top of the active layer.
 6. The lightemitting device of claim 5, further comprising a photonic crystalstructure formed on one surface thereof.
 7. A light emitting devicecomprising: a semiconductor layer; an active layer formed on thesemiconductor layer, the active layer including a plurality of quantumdots, a plurality of quantum lines, or a plurality of quantum wellstructures; an insulating layer formed on the active layer; and a metallayer formed on the insulating layer, the metal layer having a pluralityof holes formed in a surface thereof, wherein, if the quantum layerincludes quantum dots, the quantum dots comprise at least one of a groupIII-V compound semiconductor and a group II-VI compound semiconductor,wherein the holes have a diameter and a spacing of 200 nm to 1000 nm,respectively.
 8. A light emitting device comprising: a semiconductorlayer; an active layer formed on the semiconductor layer, the activelayer including a plurality of quantum dots or a plurality of quantumlines; an insulating layer formed on the active layer; and a metal layerformed on the insulating layer, further comprising a substrate, whereina stack having the semiconductor layer, the active layer, the insulatinglayer and the metal layer sequentially stacked is formed on thesubstrate, wherein the stack is a nanowire structure, wherein, if theactive layer includes quantum dots, the quantum dots comprise at leastone of a group III-V compound semiconductor and a group II-VI compoundsemiconductor.
 9. The light emitting device of claim 8, wherein theactive layer includes the plurality of quantum dots, and quantum dotscomprise a GaN-based compound.